The first set of leaves usually dont die in 2.5 weeks...

Odds are they been in the dirt or had water splashed on them with nutes.

The thing that concerns me however is that your are giving them nutes, organic or not. Its way too early for that.

#2...you have them on a flower light cycle already? At 2.5 weeks its awfully early to have them flower.

#3... a three gallon pot is way overkill for plants that age. Thats a lot of water sitting in soil that doesnt need to be there.

Post a pic...all we can do is guess without the pics.

Sounds like normal growth cycles as far as the two pea halves that first appeared and now dry and shrivel.

They feed your plants for a couple of weeks or so, then once the roots are established, they die and let the roots feed the plant.